"If you do come across a flooded roadway you do not access or try to pass those roadways."

It's a message the RACQ is echoing.

"It's not worth taking the risk of crossing flooded roads even if the water appears shallow, as it's hard to know just how deep it may be," RACQ spokeswoman Renee Smith said.

"It's far better to find an alternative route or wait until the water subsides than end up being swept away."

BOM forecasters expect scattered showers to start in Brisbane as early as Wednesday afternoon with the brunt of the wild weather to hit late Thursday night or early Friday morning. Sustained heavy rainfall should last between 24 and 36 hours in most areas.

The bureau expects the low to develop into tropical cyclone Marcia within 24 hours and make landfall near Gladstone some time Friday morning.

BOM spokesman Jess Carey said it was expected to bring winds of up to 90km/h right along the south-east coast.

"With those forecasted rainfall totals of 200-400mm, potentially localised rainfall of in excess of 500mm, if we got that rainfall over quite a short period of time, potentially that could cause some quite significant flood issues," he said.

"Of particular note to remember is we've also got dangerous surf and also high tides as well alongside that.

"Beach erosion is looking likely and beaches may be closed."

The State Disaster Coordination Centre at Kedron is open and should be fully operational from 6am Thursday.

Queensland Premier Annastacia Palaszczuk added her voice to the chorus urging residents to be prepared.

"Our message to Queensland is start getting ready now and we'll be able to provide further advice tomorrow morning," she said.

"Safety is paramount, so parents should make sure that their children do not go in to stormwater drains, into the river systems or into the rough surf that will be off the Queensland beaches."

The state Disaster Coordination Group met on Wednesday and the Queensland disaster management cabinet committee will meet on Thursday morning.

Residents in low-lying areas are being urged to prepare for potential flooding and have evacuation plans and food supplies in order.